Air scavenging system for fuel supply systems of compression ignition of engines



1961 c. L. CUMMINS 2,997,993

AIR SCAVENGING SYSTEM FOR FUEL SUPPLY SYSTEMS 0F COMPRESSION IGNITION ENGINES Filed Feb. 7, 1958 2 Sheets-Sheet 1 I I F L). W $2 L: 1 IE u- 0, 2 lhi 2 hub llllull INVENTOR CLESSIE L. CUMMINS ATTORNEY Aug. 29, 1961 c L. CUMMINS 2,997,993

AIR SCAVENGING SYSTEM FOR FUEL SUPPLY SYSTEMS OF COMPRESSION IGNITION ENGINES Filed Feb. 7, 1958 2 Sheets-Sheet 2 Ill 9 I 'IZl 93 ea 98 I00 80 14 IQ A\ 1 F16. 4 FIG. 5

INVENTOR CLESSIE L. CUMMINS United States Patent 2,997,993 AIR SCAVENGING SYSTEM FOR FUEL SUPPLY SYSTEMS 0F COMPRESSION IGNITION EN- GINES My invention relates to improvements in the fuel injectors and fuel supply system of compression ignition internal combustion engines. The invention also lends additional value and usefulness to the fuel supply apparatus shown in my Patent No. 2,670,725 and my c0- pending application S.N. 674,702 filed July 29, 1957. The invention also is applicable to spark-fired engines.

For many years the mechanical injection fuel system of a well-known type of compression ignition engine has been faced with the problem of gas or air leakage into the fuel supply lines from the combustion chamber due to a variety of causes, such as leaky check valves or wear between the plunger bore and the plunger in the injector.

Any air in the fuel supply lines has an extremely adverse effect on the performance of a compression ignition engine. Air might be forced into the fuel supply line in the injector by the great pressure diiferential developed between the combustion chamber and the fuel line in the injector when the engine is idling or is coasting, i.e. conditions when the fuel flow through the injectors is shut off or is insuflicient to wash ou the air leaking into the fuel supply lines.

Several conditions can result from air in the fuel supply lines, the most common being that after a vehicle has coasted to a stop for a trafiic signal or down a hill, the engine will not pick up and fire properly when the throttle is opened again. The length of time required for the engine to function properly again depends on how much air has entered the fuel supply lines and has to be flushed out. On a down hill coast, there is usually sufiicient momentum in the moving vehicle to keep the engine turning until the system has been cleared of air in the supply lines. Coasting to a stop as at a traffic signal is a different situation. Here the engine will probably die and the starter will have to crank it until the air has been carried out by the fuel. Either of these situations can put the vehicle and driver in dangerous predicaments as well as inconvenience to traflic on our crowded highways.

It is, therefore, one object of my invention to eliminate for good, no matter how worn the plunger or plunger bore of the injector should become, any possibility of air or gas bubbles entering into the fuel supply lines of a Cummins type mechanical injection system for a compression ignition engine.

Another problem encountered is that the area near the plunger chamber end of the injector plunger normally runs under starved lubrication conditions. Since this end of the plunger can become heated to several hundred degrees Fahrenheit, there is a great tendency for the plunger to stick and score its bore and at the very least cause one cylinder to stop firing and ruin' the injector. It is even possible for the stuck injector to cause serious damage to major components of the engine.

A further object of my invention, therefore, is to provide additional constant lubrication and thereby eliminate the problem of plungers sticking in their bore near the plunger chamber.

Another object of my invention is to provide a moat filled with the fluid used for scavenging and lubrication, with the moat located somewhere between the port of entry of the fuel to the plunger and the lower end of the plunger.

Another object of my invention is to provide an air scavenging system which is in continuous or practically continuous operation.

Another object of my invention is to provide a flow of fluid to the air scavenging system which is independent of the fuel supply in the fuel metering system.

Another object of my invention is to provide an air scavenging and lubricating system which may use any available supply of fluid and may or may not be the same fluid as is used to power the engine.

Other objects and advantages will appear from the following description and the attached drawings, in which:

In the drawings:

FIG. 1 is a diagrammatic view of a fluid supply system suitable for use with my injector, one of which is shown partly in cross section;

FIG. 2 is an enlarged view, in cross section, of the plunger and the injector housing;

FIG. 3 is a diagrammatic view of a suitable fluid pumping modification;

FIG. 4 is a view in cross section of a modification of the invention; and

FIG. 5 is a view in cross section of a plunger having a pair of check valves.

Broadly, these drawings show a fuel injection system for an internal combustion engine including a combustion chamber, an injector housing secured therein having a bore closed at its lower end to form a plunger chamber, said chamber having at least one orifice therein to distribute the fuel into said combustion chamber, an injector plunger reciprocable in said bore, means for reciprocating said plunger in said bore in predetermined timed sequence, means for feeding fuel to an inlet port in said housing, said housing being characterized by having said inlet port located up the wall of said bore, facing said plunger and spaced so that when said plunger is at the end of its retraction stroke alower portion of said plunger plugs the bore between said port and the plunger chamber; said plunger being characterized by having passage means therein which open at one end into said plunger chamber and open at the other end on the side of the plunger adjacent said inlet port in the bore wall, said latter opening being spaced on said plunger so that indexing with said irdet port occurs only when the plunger is at the end of its retraction stroke; whereby said fuel feeding means will cause fuel to enter said passage means when the plunger is at the end of its retraction stroke thereby feeding a predetermined amount of fuel into said plunger chamber, which fuel will then be forced through said orifice into said combustion chamber when the plunger is moved on its injection stroke; said housing being further characterized by having an inlet and an outlet port in the wall of said bore, facing said plunger and spaced along said wall between the aforementioned fuel feeding port and the fuel injection orifice at the bottom of the plunger chamber, said inlet port being connected to a source of fluid under pressure and said outlet port being connected to a return line for said fluid; said plunger being characterized by having a moat formed thereon in alignment with the two last-mentioned ports, whereby said moat will be kept full of fluid independent of the fuel flowing through said plunger into said plunger chamber.

In other words, what this present invention has done is to improve the fuel injection system of the mechanism disclosed in my co-pending application S.N. 674,702 filed July 29, 1957, by providing a scavenging and lubricating means which is independent of the metered fuel feeding means by including a moat on the plunger located somewhere between the port of entry of the metered fuel to the plunger and the lower end of the plunger, and having the fluid used for scavenging and lubricating fed to the moat independently of the metered fuel feeding means.

As used in this case a moat is meant to describe a channel or groove surrounding the plunger, and adapted to contain the scavenging and lubricating fluid. The moat may be a groove in the plunger or in the bore or partly in both. Fluid under pressure is introduced into the moat through a port of entry and this fluid flows from the moat through an outlet port, carrying with it any air bubbles which have worked their way from the plunger chamber up the space between the plunger and the injector bore into the moat.

The foregoing brings out a novel feature of the present invention, namely, that the fluid fed to the moat may be taken from a branch of the fuel line, but it will be from the fuel line ahead of the metering mechanism. This means that the fuel measured out by the metering mechanism does just one job, namely, to control the speed and power of the engine. At this point I should mention that with my new system of scavenging and lubricating the injection mechanisms, the fluid for this purpose may come from any suitable source and be completely divorced from the entire fuel system. For example, where a very light and volatile fuel is used, lube oil of suitable grade may be used in the scavenging system.

By providing a flow of fuel to the injector, which fuel is taken directly from the metering mechanism to the plunger chamber without any fuel being taken out of this direct line for scavenging (the latter requires a return line to the fuel sump), my system avoids the problems inherent in any system which has the metered fuel go partly to power the engine and partly to a return line back to the sump after scavenging and lubricating.

Since portions of the fuel system shown diagrammatically in FIG. 1 are described and claimed in my Patent No. 2,670,725, only those parts will be referred to here which are necessary to an understanding of its application to the present invention. These parts are described under the section headed The Fuel Supply System, which section will follow the description now of my fuel injection mechanism. Subsequently I shall describe my new and novel scavenging System shown in FIGS. 1 to 4.

The fuel injection mechanism The injector mechanism shown in FIG. 1 is a preferred form of my invention but it is understood that variations in construction proportion and dimension may be made while still retaining the essential features of the device. In FIG. 1 only one of the six injectors 72 needed in a six cylinder engine is shown. It is connected to the common :rail 36, to which the fuel is fed from the fuel supply system by a header branch 73. As shown in FIG. 2 the injector is secured in the top of the engine cylinder 74 so that its spray nozzles 75 project into the combustion chamber 76. I

The injector body 77 has a cylindrical bore 78 tapered at its lower end to form a plunger chamber 80, which chamber has a perforation 81 connected to the radially directed holes 75 forming the orifices through which the fuel is sprayed into the combustion chamber. The injector plunger 82 has a tapered end 83 to fit the end of the bore 78 in which it is reciprocable. It is pushed downwardly therein in timed sequence by the camshaft 84 and rocker arm 85. It is retracted by the spring 86.

The injector body 77 is bored to provide channels or passages 87, 88 for the feeding of fuel to the bore 78. The channel 88 terminates in fuel inlet port 90 in the wall of the bore 78 facing the plunger 82. The port 90 in the wall of the bore 78 facing the plunger 82. The port 90 is located on the bore 78 such that the scavenge groove or moat 108 lies between the port 90 and the plunger chamber 80. Not only is the supply port 98 never uncovered to the plunger chamber 80, but also it has the further protection of the moat between it and the plunger chamber. Thus, the supply port 90 is kept sacred or removed from the disturbing influence of extreme plunger chamber pressures forcing gas bubbles up the clearance between the bore 78 and plunger 82 and into the fuel supply line through port 90. A further advantage is that the supply port is located far enough up the bore wall where the injector body is thick and is not subject to distortion which would allow excessive bore clearance and wear.

Supply port 90 indexes with the grooved channel 91 in the plunger 82 when the plunger is in its retracted position where it is held by the spring 86. A cross port 92 connects passageway 93 bored axially in the plunger 82 with the groove 91.

A check valve 94 is secured to the end of a hollow shank 95 in the passageway 93 so that pressure from the combustion chamber 76 cannot force the fuel or air and gas bubbles back into the fuel supply line. The check valve seats on the beveled rim 96. The location of the shoulder 97 determines the stroke of the check valve. No spring is used to keep the valve seated as any difference in spring rates could affect the amount of fuel delivered to the several injectors. The valve is caused to seat by the inertia force resulting from the sudden downward movement of the plunger 82 and it is held seated by the pressure rise in the plunger chamber 80 during injection. Likewise on the upward stroke of the plunger 82 the inertia causes the check valve 94 to open so that by the time the fuel port 98 is aligned with the cross bore 92, there is an open passage down through the plunger, past the check valve, through passageway 99 in the plunger tip 98 and orifices 100 into the plunger chamber 80.

The orifices 188 are located in the plunger tip so that the fuel entering the plunger chamber is diverted downward into the path of the air rushing up through the passage 81 and is mixed with the air to better prepare the fuel before injection. The size and number of orifices 100 depend on the horsepower output of the engine.

Summary of the fuel injection mechanism Summarized so far, what my invention provides is a fuel injection system-for an internal combustion engine including a combustion chamber 76, an injector body 77 secured therein having a bore 78 closed at its lower end to form a plunger chamber 80, said chamber having at least one orifice 75 therein to distribute the fuel into the combustion chamber; an injector plunger 82 reciprocable in the bore 78; cam means 84 for reciprocating the plunger in the bore in predetermined timed sequence; a fuel feeding mechanism 20 for supplying fuel to an inlet port 90 in the injector body, the injector body being characterized by having the fuel inlet port 90 in the wall of the bore '78, facing the plunger 82, and spaced along the wall so that when the plunger is at the end of its retraction stroke, the inlet port 90 remains covered by the plunger, separating it from the plunger chamber 80; the plunger 82 being characterized by having passage means 91, 92, 93, 96, past the check valve 94, 99, 109 therein which open at 166 into the plunger chamber 80 and open at 91 adjacent the inlet port 90 in the bore wall, the latter opening 91 being spaced on the plunger 82 so that indexing with the inlet port 90 occurs only when the plunger 82 is at the end of its retraction stroke. In this way the fuel feeding means 20 will cause fuel to enter the passage means 91, 92, 93, 96, 99, 100 when the plunger is at the end of its retraction stroke thereby feeding a predetermined amount of fuel into the plunger chamber 80, which fuel will be forced through the orifice '81, 75 into the combustion chamber 76 when the plunger 82 is moved on its injection stroke.

The fuel supply system While the injector mechanism set forth herein is adapted for use with various forms of fuel feeding devices, it is particularly suited to use with the fuel supply system of my Patent No. 2,670,725, which I have shown only diagrammatically in FIG. 1 of the drawings of this present case.

The fuel apparatus may include, as a means to conduct fuel to the engine, either a distributor by which flow to the respective injectors 72 is determined or may omit the distributor and have the fuel injectors for the respectivecylinders connected to a common rail which in turn is connected to the fuel supply or conduit. In the case where a distributor is utilized, the period of overlap between a supply passage in the distributor and each of the passages leading to the respective injectors determines the time factor. In the case where the distributor is eliminated, each of the fuel injectors is provided with a cam operated plunger 82 which opens and closes a supply port 90 in the injector in timed relation to the operation of the engine, and thus determines the time of opening.

In a fuel supply apparatus of the character herein contemplated where the fuel is maintained under constant pressure, a constant area of opening for the metering orifice would result in a greater fuel delivery to the engine as its speed decreases. This fact becomes evident in considering a distributor since the time during which the supply passage and each of the passages leading to the cylinders are overlapping increases with a decrease in engine speed. Similarly, the time that the supply port 90 in an injector is opened by the plunger is increased as the speed of the engine decreases. As a result, when the engine speed is pulled down by an increased load for a given throttle setting, the engine torque curve would rise above acceptable limits under such conditions, and thus overload the engine.

The invention of my Patent 2,670,725 overcomes this difrlculty by providing a variable orifice in the line between a source of fuel under constant pressure and the distributor or fuel injectors, as the case may be, with the effective area of the variable orifice regulated by a governor to so control the fuel flow to the engine that any desired torque at maximum throttle opening may be obtained throughout the speed range of the engine. Such variable orifice may be provided by a needle or other type valve operable by the governor and connected with another variable orifice provided by a second needle or other type valve, also under control of the governor but acting oppositely to the first mentioned valve and operable to deter-mine the maximum speed of the engine. In series with these two valves is a manually operable throttle which may also have the form of a needle valve. The apparatus is also so arranged that an idling speed control is provided, which is connected to the governor for automatic operation.

While my present fuel injection mechanism is illustrated in an embodiment like Patent No. 2,670,725 in which the fuel is maintained under substantially constant pressure throughout the speed range of the engine, the invention is equally applicable to a fuel pressure which may be varied with the engine speed but is constant for any given speed, and in that case the shape of the first mentioned needle valve is varied to compensate for such variation in pressure. The term constant pressure as used is therefore in the broader sense and is not limited to the idea of a constant pressure throughout the speed range of the engine.

The fuel supply system shown diagrammatically in FIG. 1 is of such form that it may be mounted at any convenient location on the engine and may comprise a main casing or housing 20, a pump casing 21 with the governor mounted on the housing 20. Fuel for the engine is adapted to be drawn from a fuel supply tank (not shown) through piping adapted to be connected to a fitting 22 carried by the pump casing and leading to the intake passage 23 of a pump 24 which may be of the gear type or other suitable form. The gear pump 24 discharges fuel into a passage 25 adapted to drain into a float tank 26. The float tank "26 is provided with a float controlled valve 27 to shut off the how of fuel supplied by the pump 24 when the fuel in the float chamber reaches a predetermined level. When the valve 27 closes the discharge passage 25, a relief passage 28 controlled by a pressure relief valve 30 permits the fuel delivered by the pump 24 to be returned to the intake side thereof. It is important to remember that the pump 24, relief valve 30 and float chamber 26 with the float valve 27 are not essential to the system and may be eliminated when desired. The float chamber 26 then becomes the source of fuel.

The source of fuel under constant pressure in the present instance comprises a second pump 31 herein illustrated as a gear pump having passages 32, 33 for returning the fuel, in excess of that used by the engine and for scavenging, to the intake side of the pump 31 with a pressure regulator 34 mounted in the passage 33. The pressure regulator 34 is of the type which maintains the pressure of the fuel at the delivery side of the pump 31 at a substantially constant value so that there will be little variation in pressure to affect the flow of fuel through the remainder of the apparatus.

From the pump 31, fuel flows through the conduit means provided by passages formed chiefly in the main housing 20, to the respective injectors 72, and the flow is controlled by valve means mounted in such passages. The main conduit or passage 35 extends from the second gear pump 31 and is connected to the common rail 36 through a series of valves. Thus the main conduit 35 has a manually operable valve in the form of a needle valve 37 which constitutes the throttle for the engine. Beyond the throttle 37, the main passage is extended, as at 38, to open into a valve chamber 40. In the latter is a governor-controlled valve 41, also in the form of a needle valve, cooperating with the opening of the passage 38 into the chamber 40 to provide a variable orifice. From the needle valve 41 the main pasage is still further extended, as at 42, to open into a valve chamber 43 having a third needle valve 44 mounted therein, which is also governor-controlled. The needle valve 44 cooperates with the opening of the passage 42 into the chamber 43 to provide another variable orifice. From the latter, the main passage continues, as at 45, 46, 47 to the common rail 36 with a shut-off valve 48 placed in the continuation 45.

As mentioned above, both the valve 41 and the valve 44 are under the control of the governor, which is here indicated at 50. The governor 50' is illustrated as comprising a pair of centrifugal weights 51 pivotally carried by a rotating head 52 mounted on and driven by a main shaft 53. The drive shaft 53 is journaled in the governor casing to the left of casing 20 and is there provided with means (not shown) adapted to be connected to and driven by the engine.

The governor weights 51 are provided with inwardly turned fingers 54 adapted to engage a collar 55 mounted on a stub shaft near its end. The governor weights 51 are so positioned that as the sped of the engine increases and the weights tend to move outward, the collar 55 will be moved to the left. Resisting such movement of the collar is a spring means, indicated generally at 56, and interposed between the collar 55 and the driving head 52. The collar 55 includes a sleeve 57 on which are provided a pair of spaced flanges 58 and 60. Mounted above the flanges 58 and 60 in the casing 20 and extending transversely to the drive shaft 53 is a rock shaft 61, journaled at its ends in the casing 20. Secured on the rock shaft 61, intermediate its ends, is a rock lever or yoke having a pair of spaced arms 62 embracing the drive shaft and having rollers 63 mounted on their ends and engaging in the groove formed by the flanges 58 and 60.

Thus, as the governor weights 51 move inwardly or outwardly in response to variations in the speed of the engine, the rock shaft 61 will be actuated in opposite directions, depending upon the changes in engine speed.

Secured to the rock shaft 61, adjacent the ends thereof 7 and on opposite sides of the main drive shaft 53, are a pair of levers 64 and 65, the lever 64 extending upwardly and engaging the end of the needle valve 44, while the lever 65 extends downwardly from the rock shaft and engages the end of the needle valve 41. Thus, the levers 64 and 65, as they are rocked by the rock shaft 61, will move the needle valves 44 and 41 toward their closed positions, depending upon the direction of rotation of the rock shaft. To move the needle valves 44 and 41 in an opening direction, springs 66 are mounted about the adjacent ends of the needle valves and hear at one end against the main housing and at their other ends against collars 67 provided on the ends of the valves.

It will be evident from the foregoing, and by an inspection of FIG. 1, that when the engine speed increases and the governor weights 51 move outwardly, the rocker arm 64 will move the needle valve 44 toward its closed position against the resistance of its spring 66, while the rocker arm 65 will move in a direction permitting the spring 66 on the needle valve 41 to move the latter toward an open position. Thus, the two needle valves 44 and 41 are moved oppositely in response to changes in engine speed. Since the needle valve 44 is moved toward a closed position as the engine speed increases, such valve is utilized to determine the maximum speed of the engine. Thus, the needle valve 44 will close sufficiently to decrease the flow of fuel to the engine through the main conduit when the engine speed closely approaches its maximum and will eventually completely close the main conduit to prevent all flow of fuel to the engine and thus limit its speed. It is obvious, of course, that as soon as the speed falls below its maximum, the needle valve 44 will open to again permit flow through the main conduit.

For a given setting of the various valves in the system, the amount of fuel delivered to the engine would increase with a decrease in engine speed. This would obviously cause the torque curve of the engine to rise on decreasing engine speed and if the engine were operating at full throttle, it would cause excessive overloading of the engine. By means of the valve 41, such a condition is compensated for to a predetermined extent so that the resultant torque curve of the engine may be of a predetermined character and preferably is substantially a fiat curve with only a slight increase in torque as the engine speed decreases. While the valve 41 may be so constructed as to give any desired shape to such curve, the foregoing shape is preferred, although in some instances it may be more desirable to cause the torque to fall off at lower engine speeds.

In the present construction, the needle valve 41 moves toward its closed position as the engine speed decreases. Consequently, the flow of fuel through the main conduit may thereby be decreased, upon decrease in engine speed, to compensate for the tendency toward increased flow due to the longer period of opening in the injectors. The extent of compensation thereby obtained may be predetermined by so shaping the valve 41 as to provide a given area of flow about the needle valve for any given engine speed. The valve 41 may also be shaped to compensate for variations in pressure of the fuel.

The throttle valve 37 may be opened to any desired extent to control the speed of the engine. If opened to its full throttle position, the'valves 41 and 44 will exercise the necessary control over the flow of the fuel. Thus, with the throttle 37 fully opened, if the load on the engine is light and the speed thereof tends to exceed the desired maximum, the governor '50 in response to such speed will shift the needle valve 44 toward its closed position to decrease the flow of fuel and ultimately to stop the flow of fuel so that the speed of the engine cannot exceed a desired maximum. However, if the load on the engine increases, when the throttle 37 is fully opened, the engine speed will tend to decrease, but

creased time of indexing of the port in the injectors will be compensated for by the needle valve 41, which decreases the flow of fuel with a decrease in engine speed.

The common rail 36, as heretofore mentioned, is connected to the respective engine cylinders through injectors, one of which is indicated at 72 in FIG. 1. The fuel is delivered to each injector through an inlet port 90, the opening of which is controlled by a plunger 82 operated by the engine camshaft 84.

Each injector cam 84 is so designed that the period of time during which the port 90 is opened by the plunger '82 determines the time in which fuel is supplied to the cylinder. Since the plunger -82 is thus operated in timed relation to the speed of the engine, the

period of time during which the port 90 is open increases with a decrease in engine speed. The needle valve 41, however, in this instance, under the control of the governor, compensates for the variation in the time caused by changes in engine speed. The several plungers 82 in their respective injectors 72 are, of course, opened and closed sequentially and the opening of two or more injectors may overlap if desired.

The fuel control apparatus also includes means for providing a governed idling speed control for the engine. To this end, a by-pass 68 extends from the main conduit '35 around the throttle 37 to the needle valve 41 so that the fuel may flow through the passage 68, when the throttle 37 is closed, to operate the engine at idle speed. The by-pass passage 68 opens into the bore in which the needle valve 41 is mounted at a point spaced from the tapered end of the needle valve, and a groove 70 is formed in the needle valve 41 at a point which registers with the opening of the passage 68 when the engine is operating at idle speed. Extending from the groove 70 is a diagonal passage 71 formed in the needle valve 41 and opening into the valve chamber 40 in which the needle valve 41 is located. At this time, since the engine speed is low, the needle valve 44 is in its fully opened position. Thus, sufficient fuel may flow from the pump 31 through the by-pass passage 68 to the groove 70 and the passage 71 in the needle valve to operate the engine at idle speed. Should the engine speed tend to increase slightly above the desired idle speed, the needle valve 41 will bemoved by the governor to the left, and flow through the passage 71 in the needle valve will be decreased and eventually cut off by the movement of the needle valve to shift the passage 71 out of communication with the valve chamber 40. When the speed of the engine has decreased sufficiently, the needle valve 41 will be moved to the right to again permit flow through the passage 71. The engine will thus be maintained at idle speed under the control of the governor S0.

The scavenger and plunger lubrication circuit A part of the fuel flow from the pump 31 is diverted into the conduit 101 before reaching the metering section of the fuel supply system. The flow rate and line pressure are greatly reduced by a restricting orifice or valve 102 as very little fluid is required to accomplish the necessary scavenging of air or gas bubbles leaking up the plunger bore 78 from the plunger chamber 80 in the injector. Also very little fluid flow is required for lubrication. After passing the restriction 102, the scavenge circuit continues through conduit 103, common header 104, branch header 105 into each injector body 72. It then continues through passageway 106, intake port 107 and into the moat or circular groove 108 around the plunger 82. Preferably groove 108 is of an axial length such that intake port 107 and discharge port 110 which are opposite each other will always be indexed with the groove 108 whether the plunger 82 is any tendency .for increased flow of fuel due to the in- .15 up .or down. .1" his assures that any air ;or gas bubbles leaking past the lower extremity of the plunger 82 from the plunger chamber 80 will be flushed away through the discharge port 110 by the small flow of fluid coming through the intake port 107 and around the groove 8. The fluid (in this case fuel) with the entrained air leaves the injector through passageway 111, shown leaving the injector body 72 at its lower end for clarity of drawing. The scavenge circuit then continues through common header 112, conduit 113, 114 and returns to the float chamber or tank 26. Thus air which normally might have leaked between the plunger 82 and its bore 78 has been carried away before it could enter the metered fuel supply system and cause trouble.

It will thus be seen that the scavenge circuit (a) wastes no fuel when coasting; (b) lubricates and cools the plunger mechanism by circulating fuel therein when coasting as well as pulling; (c) scavenges any air bubbles reaching the plunger by entraining them in the scavenge circuit fuel being returned to the sump 26; (d) avoids any dependence on resistance pressures in a fuel return line which could influence the rate of feed to the injectors; (e) and simplifies the supply of fuel for scavenging air bubbles and lubricating the injector plungers by bypassing the governor and throttle control means; and (f) separates the function of lubrication and scavenging from the fuel feeding operation.

It will also be seen from the above that in my system when the engine is producing power, only the amount of fuel is fed to the injectors that will -be injected into the engine cylinders. In other words, in my system I do not feed an excess of fuel, use part of it to power the engine and return the unused portion to the fuel source. It will now be clear that where this latter system is used, if anything occurs to block or restrict the surplus or unused portion of the fuel in its return to the fuel source, the surplus fuel will be backed up and will be injected into the engine, causing it to run wild. Not only can this not happen in the present system, but by keeping the scavenge line separate from the fuel supply line, I relieve the installer of the engine from having to take into account or pay any attention to the size of the fuel return piping, the size of the vent in the fuel tank, or whether there are any restrictions in this piping.

Earlier I mentioned that the fluid entering the conduit 103 for the scavenging and lubricating function need not necessarily come from the fuel supply source, and that the fluid may be a lube oil of suitable characteristics. In this case, a suitable pumping means (FIG. 3) to force the desired fluidunder the necessary pressure will be connected to the conduit 103 and the sump or tank 120 from which this pump draws will be connected to the fluid return line 114.

A third alternative to using fuel oil in the scavenging and lubricating system is to use lubricating oil from the engine lubricating supply. In that case, a suitable takeoff from the engine is connected to the conduit 101. The pressure reducer 102 is set to give the required pressure in the conduit 103. After the lube oil has gone through the moat 108 and out the return line 111, it can empty directly intto the rocker arm housing from whence it will flow back to the crankcase.

It will also be seen from the above that with the moat the problem of having the plungers stick or wear during coasting is eliminated, and that they are kept freshly lubricated and cooled when the engine is being motored during coasting or when the engine is under power.

In FIG. 4, I have shown a modification of the injector body 77 and of the scavenging fuel return line 111 to care for the contingency of dirty fuel temporarily preventing the check valve 94 from seating properly and admitting air into the passage 93, which air interferes with proper operation when the next fuel charge is introduced as the port 91 aligns with the fuel entry port 90. This includes adding a passageway 121 between the wall of the bore 78 and the return line 111. The passageway 121 is positioned along the wall of the bore so it will align with theport 91 when the plunger 82 is in its lowermost position.

While I have indicated above that lack of a spring in the check valve does not affect running of the engine, there are circumstances where I prefer to provide a spring-held check valve in the injector plunger. This spring preferably is just strong enough to hold the check valve closed when the engine is not running. On the down stroke of the plunger, the inertia and pressure in the plunger chamber hold the check valve closed. On the upstroke of the plunger the inertia opens the check valve regardless of the spring. Thus the check valve is principally inertia operated, which is important because it removes any dependency on equal strength springs to achieve equal fuel distribution. The spring will serve primarily to hold any fuel in the plunger and injector body when the engine is shut down. Several advantages flow from this: First, fuel is saved by its not draining into the combustion chamber when the engine is at rest. Second, in starting, the plunger being full of fuel starts injecting immediately. Third, fuel if allowed to drain into the combustion chamber will, when the engine is next started, smoulder on top of the piston and emit a steamy exhaust of considerable volume until consumed.

One form of spring pressed check valve means is shown in FIG. 4 where the spring 122 is fitted into the annular space 123 between the head of the check valve 94 and the shoulder 125.

Another form of spring pressed check valve means includes two check valves 126 and 1 27 in FIG. 5. Check valve 126 is similar to check valve 94 in FIG. 4 and needs no further description. Check valve 127 is located at the lower end of the plunger and when seated will trap any fuel between it and the upper check valve. The springs 128 and 130 are each light enough not to interfere with the inertia operation of the check valves as explained above, and need only be stiff enough to close the check valves 126 and 127 when the engine is at rest.

It all be understood that other modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

I claim as my invention:

1. In a fuel system for an injection type internal combustion engine having one or more cylinders, each with a piston reciprocable therein, injector means for each cylinder, means for actuating each injector means in timed relation to movement of the piston in its cylinder, each said injector means being characterized by having a housing which is insertable in its related cylinder, said housing having a pressure chamber at one end and an outlet therefrom into said cylinder; a plunger reciprocable in a bore in said housing, said plunger having a passageway therein communicating at one end with said pressure chamber and at its other end with a fuel supply source; means for feeding combustion fuel to said source; said plunger and bore also having a radial moat formed between them along their mating faces between said pressure chamber end and said fuel supply source; and means for circulating a fluid in said moat when said engine is in use, which fluid is at no time in communication with said combustion fuel passing to said fuel supply source, whereby any air which is forced back from the cylinder through the pressure chamber into the space between the plunger and the bore will be entrained in the fluid in the moat before it can reach the fuel supply passageway.

2. The device of claim 1 in which the means for feeding fuel for combustion to said plungers is independent of the means for circulating fluid in said moat.

3. The device of claim 1 in which there is a return line from said moat back to the fluid source to carry away from the moat any air bubbles that may collect in the moat.

4. The device of claim 1 in which the moat is formed by an annular groove in said plunger and mating fluid feed means is formed in the bore wall in line with the moat. I

5. A fuel injection system for compression ignition engines of one or more cylinders, having a piston reciprocable in each cylinder and a fuel measuring means, said system being characterized by an injector housing mounted with its spray nozzle in communication with its related cylinder, said housing having two separate non-communicating fluid passageways, one being connected to the fuel measuring system of said engine, and having a combustion fuel feed port, the other being connected to a source of fluid under pressure, and having a fluid feed port located between said spray nozzle and said fuel feed port; an injector plunger reciprocable in a bore in said injector housing, said plunger having in its body a conduit extending from its end adjacent the spray nozzle to a port in an annular groove formed therein to align with the combustion fuel feed port in said injector housing when said plunger is in retracted position; said plunger also having an annular groove formed therein to align with said fluid feed port, whereby said groove is maintained full of fluid at all times.

6. The device of claim in which the axial extent of the last mentioned annular groove is sufficient to maintain communication between the groove and the fluid feed port during the full reciprocating working stroke of said plunger. 3 v v 7. The device of claim 5 in which there is a port in said housing in line with said last mentioned annular groove and connected to a return line back to the fluid feed source. V

8. A fuel injection system for an internal combustion engine including a combustion chamber, an injector housing secured therein having a bore closed at its lower end to form a plunger chamber, said chamber having at least one orifice therein to distribute the fuel into said combustion chamber, an injector plunger reciprocable in said bore, means for reciprocating said plunger in said bore in predetermined timed sequence, means for feeding fuel, to an inlet port in said housing, said housing being characterized by having said inlet port locatedrup the wall of said bore, facing said plunger and spaced so -that when said plunger is atthe end of its retraction stroke, a lower portionof said plunger plugs the bore between said port and the plunger chamber; said plunger being characterized by having passage means therein which open at one end into said plunger chamber and open at the other endon the side of the plunger adjacent said inletport in the bore wall, said .latter opening being spaced on said plunger so that indexing with said inlet port occurs only when the plunger is at the end of its retraction stroke; whereby said fuel feeding means will cause fuel to enter said passage means when the plunger is at the end of its retraction stroke thereby feeding a predetermined amount of fuel into said plunger chamber, which fuel will then be forced through said orifice into said combustion chamber when the plunger is moved on its injection stroke; said housing being further characterized by having an inlet and an outlet port in the wall of said bore, facing said plunger and spaced along said wall between the aforementioned fuel feeding port and the fuel injection orifice at the bottom of the plunger chamber, said inlet port being connected to a source of fluid under pressure and said outlet port being connected to a return line for said fluid; said plunger being characterized by having a moat formed thereon in alignment with the two last-mentioned ports, whereby said moat will be kept f-ull of fluid independent of the fuel flowing through said plunger into said plunger chamber.

9. A fuel injector mechanism, adapted for use in an internal combustion engine having a cam shaft and plunger actuating means moved thereby, said mechanism comprising a fixed housing having a bore therein; a spray nozzle at one end of said bore; an injector plunger reciprocally mounted in said bore, said plunger having an axially extending passageway therein open at one end near said spray nozzle and in communication at the other end. with an annular groove formed in said plunger; a fuel feed port in said bore in line with said groove when said plunger is in its retracted position; check valve means in said plunger passageway adapted to be principally inertia operated and to be held closed by injection and combustion chamber pressures; and resilient means for holding said check valve means closed when the engine is at rest, so that fuel will not flow down said passageway into said cylinder should said engine, when at rest, stop with said annular groove and fuel feed port aligned.

10. The device of claim 9 in which said check valve means includes doublecheck valves.

References Cited in the file of this patent UNITED STATES PATENTS 1,749,975 -Grofl Mar. 11, 1930 1,828,792 Tverbakk Oct. 27, 1931 1,995,459 Olsen Mar. 26, 1935 2,317,618 King Apr. 27, 1943 2,700,342 French J an. 25, 1955 2,799,535 French July 16,1957 2,838,037 French June 10, 1958 

